The stark contrast in the manner of the two departure, one after 12 months and the other within 48 hours of allegations first surfacing, struck politicians from all parties.
Mr Mandelson's resignation came as a shock to MPs who believed he had carried out a reasonably efficient damage-limitation exercise in a series of media interviews on Tuesday.
Even left-wingers, many of whom had rubbed their hands with glee at the former secretary of state's discomfort, were impressed by his swift decision. But the delays over Mr Robinson's removal won him few friends.
The deputy Tory leader, Peter Lilley, called for a full and independent inquiry into the events and claimed that it was "extraordinary" that the Prime Minister had not concluded in both cases that rules had been broken. "The whole affair has shown that ministers have gone out of their way to hide their links with Geoffrey Robinson. We now need clear assurances that no other minister has received any kinds of financial support from him or owe him any obligations for any support he has given them."
Other members of the Shadow Cabinet were less statesmanlike in private. "We can hardly believe our luck," said one. "Christmas has come early," said another.
The Liberal Democrat leader, Paddy Ashdown, who saw Mr Mandelson as a key ally in his grand project to realign the left of British politics, said he had made an "honourable and correct" decision to resign. "All of us who value probity and the conduct of public duty would like to think that we would have done the same thing. We have almost forgotten what it is like to see ministers resigning," he said.
The Liberal Democrat MP Charles Kennedy, a member of the Commons Standards and Privileges Committee that reprimanded Mr Robinson over aspects of his business affairs, said the minister's 55-second apology to the House proved he had to go.
That apology was inadequate and subsequently he and Peter Mandelson became like two rock climbers tied together against the face of overwhelming odds. When one fell, it came as no surprise that both would be dragged down."
Paul Flynn, Labour MP for Newport West, said the resignations had finally succeeded in clearing out the "mess" that had dogged the Government. "It's right they should go. After the Bernie Ecclestone affair and Derek Draper, we are losing that reputation as a sleaze-free party," he said.
"There's a feeling that we are too fond of luxury lifestyles and we are too close to big business and lobbyists. We should put some clear pink water between ourselves and them."
Clive Soley, chairman of the Parliamentary Labour Party, said many MPs would regret Mr Mandelson's resignation but saw Mr Robinson's departure as inevitable. "The party will be sad about losing Peter's talents, but there is an element of reassurance around that we are serious about living up to the high standards we set ourselves."
Rhodri Morgan, MP for Cardiff West and a leading contender for First Secretary of the Welsh Assembly, said Tony Blair's decision to accept Mr Mandelson's resignation must have been his most difficult to date. "We are all going to sleep easier because if it had carried on festering horrendously over Christmas the Government would have suffered," he said.
Martin Bell, the Independent MP for Tatton elected on an anti-sleaze ticket, said of Mr Mandelson: "Common sense tells you that when you get a loan of this size, you declare it - that's the lesson to all MPs, if in doubt, declare it."
The author and journalist, Robert Harris, one of Mr Mandelson's closest friends,said that he was sure the former secretary of state would one day return to front-line politics. "He'll be back because he is such a political animal and he's so important in a party not exactly budding with talent. After a suitable penance, he can return."
However, the enmities stirred up by Mr Mandelson's abrasive political style, together with continuing inquiries into the loan deal, make a speedy comeback improbable.
One union official, who refused to be named, reflected the anger felt by some in the labour movement over plans to water down the Government's plans for union recognition.
"Mandelson has done us no favours over the last few months and I am sure a lot of ordinary trade unionists will be very happy to see him go," he said.Reuse content